In 2005, cardiologist Barbara Natterson-Horowitz was called to the zoo to examine a non-human patient, an emperor tamarin with heart failure. She was surprised when the veterinarian told her not to look her patient in the eyes because eye contact could cause capture myopathy. In this condition, when an animal is captured, restrained, and feels threatened, there is a catastrophic surge of adrenaline that damages muscle tissues and can kill. It was described decades ago, but medical doctors don’t read the veterinary literature. It wasn’t until the early 2000s that American doctors began to recognize a similar phenomenon in human patients, takotsubo or stress-induced cardiomyopathy.

She began to wonder whether animals got other human diseases. She quickly learned that they did. Jaguars get breast cancer and may carry the same BRCA1 gene that plagues Ashkenazi Jewish women, rhinos get leukemia, penguins get melanoma, gorillas die from ruptured aortas, and koalas are in the midst of an epidemic of sexually transmitted chlamydia. Wild dragonflies infected with parasites become obese and develop a form of metabolic syndrome. Pretty much every human disorder occurs in animals too.